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Homemade Electronic Shifting [WIP]

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Homemade Electronic Shifting [WIP]

Old 03-07-10, 01:23 PM
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Servo888
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Homemade Electronic Shifting [WIP]

WIP = Work In Progress.

Okay guys and gals! I haven't been riding this winter (spinning classes ftw), even though I have my tights, cold weather coats. I just hate the cold. So instead, I have a bike related winter project. This year, I'm working on building my own version of electronic shifting. I'm documenting the process on my website:

https://www.veescafe.com/openshift/

The idea is to make an electronic STI rig using inexpensive parts, such as servos, zip ties, and a simple micro controller. I'm planning on spending around $150 out of pocket by the time I'm done. It's still early in the build (two weeks in), and I'm waiting for parts to come in; but I've made good progress. Here's my micro controller moving the servo arm at a push of a button:

https://www.youtube.com/watch?v=Ly5aSqmeAeM




So let me know what you think! I'm actually very excited about this project. Even if it fails, the fun factor is pretty large.

___________________________
UPDATE 1!
After much time spent trying to get the servo to work using a spring, cable, etc. I've determined that that method would would not work. The issue is that there is too much drag for the servo to operate smoothly; drag = battery drain. . Yesterday, I took a dremel to the rear derailleur, used some double sided tape, a tie wrap, and some lead free solder (it's very malleable) to create something that actually moved!

https://www.youtube.com/watch?v=cudEbXKiefA

I'm thinking this is the right way to go with the build. I'll drive down to the hobby shop and try to find some parts to replicate the prototype with something less ghetto.

___________________________
UPDATE 2!
Yikes, it took most of this weekend to get my rear derailleur remotely functional. Basically, I spent most of my time wrapping my head on how the heck to connect the servo to the derailleur. After two failed attempts, and lots of epoxy, I got a very functional derailleur. The video here is:

https://www.youtube.com/watch?v=m23kgfQIl7E

It's far from pretty (I'm going to remove the blue painters tape, and give it some paint once I get it working right), but it seems to be functioning correctly. The best part is that it seems to be able to carry a good amount of load, and there is no binding. I can't wait to strap it to the bike and give it go with a chain on. For now, I'll let the epoxy cure, and update my build log with pictures. Hopefully next weekend I'll get it mounted up.

updated build log:
https://www.veescafe.com/openshift/Log03142010.aspx

___________________________
UPDATE 3!
Not too big of an update, mainly did some work on the front derailleur, and started work on building the electronics.

updated build log:
https://www.veescafe.com/openshift/Log03252010.aspx




___________________________
UPDATE 4! 3/28/2010
This weekend I finished up on the electronics; though I still need to find some suitable buttons to use. The whole system now can run off the battery pack; can't wait to get connect up to the bike!



Updated build log:
https://www.veescafe.com/openshift/Log03282010.aspx

___________________________
UPDATE 5! 4/4/2010
I haven't finished my build log for this week; hopefully I'll get it done in the new few days. But, I wanted to share what I've done so far; believe it or not, it's actually running!

https://www.youtube.com/watch?v=xXwDmX9Ly_U



Build log added 4/6/2010: https://www.veescafe.com/openshift/Log04062010.aspx
Enjoy!

Last edited by Servo888; 04-06-10 at 07:49 PM.
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Old 03-07-10, 01:31 PM
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what kind of servos and what voltage would you be running? i'd think you would need hitec 7955TG ($115 each. we used to run between 5 and 15 of them in our RC airplanes) servos and even then, I don't know how they would handle the load by having to hold the arm off center to keep the bike in gear. you might have better luck with a screw type servo but I don't know how fast they are on the economical end.
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Old 03-07-10, 01:39 PM
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Originally Posted by Yaniel View Post
what kind of servos and what voltage would you be running? i'd think you would need hitec 7955TG ($115 each. we used to run between 5 and 15 of them in our RC airplanes) servos and even then, I don't know how they would handle the load by having to hold the arm off center to keep the bike in gear. you might have better luck with a screw type servo but I don't know how fast they are on the economical end.
12 volt power pack based on 8 NiMH AA batteries with 6 volts to the servos. And I'll be running Chinese made mg955 high torque servos (~$12/each). Load is not a problem when you remove the return spring. I have an explaination of the process on my website; here's a picture (note the missing spring):

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Old 03-07-10, 02:48 PM
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Good luck with your project, I think in the long run those servos will not have the power to actually shift under load (they may move) and if they do over a short time the plastic gears will fail. I have quite a bit of experience with 1/4 scale servos in Nitro powered boats and those servos are not made that good for something as abusive as that. But have fun....
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Old 03-07-10, 03:19 PM
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Very cool. Great effort and imagination.
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Old 03-07-10, 03:31 PM
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Originally Posted by scotch View Post
Very cool. Great effort and imagination.

Agree. Keep us posted.
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Old 03-07-10, 03:31 PM
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Fun project - good luck with it. RC servos are amazing little things, and as that German guy appears to have demonstrated, this is certainly feasible.
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Old 03-07-10, 03:36 PM
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I would go with a cheap lipo or a123 packs. the nihm won't make as much power, plus the power tends to taper off as the drain. the lipo or a123 would be just a little more expensive, and provide more linear power. if yo decide to go to higher end servos later in the build, some of the newer servos, like some JR's can take 12 volts which would provide enough tq and speed to shift with no problem under load, along with no plastic on the side.
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Old 03-07-10, 03:38 PM
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Originally Posted by JTGraphics View Post
Good luck with your project, I think in the long run those servos will not have the power to actually shift under load (they may move) and if they do over a short time the plastic gears will fail. I have quite a bit of experience with 1/4 scale servos in Nitro powered boats and those servos are not made that good for something as abusive as that. But have fun....
I don't know how abusive the boats are, but the 90 size helis and 35%+ planes beat the heck out of servos and the market has kept up with the needs. a lot of the newer servos for those applications are extremely powerful and durable with things like titanium gears.
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Old 03-07-10, 04:22 PM
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With all the questions about what type of servos you're using, how is Di2 set up?
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Old 03-07-10, 04:29 PM
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Originally Posted by tadawdy View Post
With all the questions about what type of servos you're using, how is Di2 set up?
Or the old mavic system from 15 years ago?
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Old 03-07-10, 06:10 PM
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are you trying to do an auto trim, a human controlled trim system, or no trim at all? And i take it you are going for the press the button and shift, not the crazy Di2 wait until just the right moment shift stuff right?
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Old 03-07-10, 06:42 PM
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if you want to get really into it, you could probably wire up a trim system through a receiver and transmitter (custom of course) when i used to run rc helis i learned one thing, dont skimp on servos. blew a 2000 nitro heli due to bad servos. i would also probably make my own battery with individual cells (like high end electric 1/10 scale cars use)

god speed
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Old 03-07-10, 08:01 PM
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What if you keep the return spring, but had a cable that winds onto a reel using the servo? That way, each time the servo rotates, it's the same distance as the portion of the circumference, which doesn't change with the angle. It would solve the problem of trying to figure out how much rotation distance translates into linear distance based on the angle of the arm. Here's my attempt to illustrate it:
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Old 03-07-10, 10:00 PM
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Nice one : )

Might be a thought to use one of those old Exage derailleurs with the clamp bolt on a sprung arm; that'd save your servo.
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Old 03-07-10, 11:11 PM
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I saw on your website you were talking about needing a solution to check to make sure the input voltage is high enough. Take a look at the link below. It could probably be used to reset the controller if the voltage drops too low. Also, I know the Arduino website says that the Nano takes an input range of 6-20V, but I would think it would work down to 5V since it works on usb, which is 5v. I have never damaged a microcontroller from low voltage, but try it out at your own risk. If the voltage goes too low, I have had problems with output/input logic level 1 never reaching high enough voltage to register, so you remain the gray area where the controller may or may not read correctly.

https://www.goldmine-elec-products.co...?number=A10088

On a bike related side, what are the benefits of electronic shifting over manual shifting other than the fact you can say you have electronic shifting?
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Old 03-07-10, 11:40 PM
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Given the above, I'd say don't worry about voltage regulation unless the Arduino dies; it's only thirty bucks.
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Old 03-08-10, 12:14 AM
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you guys are talkin in some crazy code words I've never even heard of
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Old 03-08-10, 01:53 AM
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Originally Posted by daodedick View Post
What if you keep the return spring, but had a cable that winds onto a reel using the servo? That way, each time the servo rotates, it's the same distance as the portion of the circumference, which doesn't change with the angle. It would solve the problem of trying to figure out how much rotation distance translates into linear distance based on the angle of the arm.
Because it would be so much more fun to do all of the trig, and then program for the different rotations!!!!
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Old 03-08-10, 02:22 AM
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I guess I just don't understand the point of this. The disavantages of both cables and electronics but he advanatges of neither.
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Old 03-08-10, 02:43 AM
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The cable's like a foot long; I doubt the disadvantages figure.

And why don't the ability to change gear at the touch of a button and automatic FD trimming matter?
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Old 03-09-10, 06:33 AM
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Good Lord, he's having fun and it's interesting. Does there have to be a point?
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Old 03-09-10, 07:06 AM
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Originally Posted by umd View Post
I guess I just don't understand the point of this. The disavantages of both cables and electronics but he advanatges of neither.
https://www.michigansnowcams.com/

I guess.
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Old 03-09-10, 12:16 PM
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This will be very difficult to achieve without a basic understanding of the mechanism of index shifting
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Old 03-09-10, 08:13 PM
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Originally Posted by Yaniel View Post
I would go with a cheap lipo or a123 packs. the nihm won't make as much power, plus the power tends to taper off as the drain.
I'm too afraid of those packs; I'll probably end up burning down my house. . If this project works out, the lipo / a123 upgrade will be a must. Those babies weigh 30% less, and last much longer.

Originally Posted by tadawdy
With all the questions about what type of servos you're using, how is Di2 set up?
Basically they put the guts of a servo (motor, gears, potentiometer) right inside the derailleur. I would love to take one apart to see how everything works.

Originally Posted by sirious94
are you trying to do an auto trim, a human controlled trim system, or no trim at all? And i take it you are going for the press the button and shift, not the crazy Di2 wait until just the right moment shift stuff right?
Auto trim on the front derailleur will be there, as well as an 'over-shift' feature. Basically; the derailleur will guide the chain slightly beyond the sprocket to allow the chain to fully engage.

Originally Posted by daodedick
What if you keep the return spring, but had a cable that winds onto a reel using the servo? That way, each time the servo rotates, it's the same distance as the portion of the circumference, which doesn't change with the angle. It would solve the problem of trying to figure out how much rotation distance translates into linear distance based on the angle of the arm. Here's my attempt to illustrate it:
This is a very good idea! I'll see if I can locate some quality pulleys to experiment with.


Originally Posted by adclark
... Take a look at the link below. It could probably be used to reset the controller if the voltage drops too low...

On a bike related side, what are the benefits of electronic shifting over manual shifting other than the fact you can say you have electronic shifting?
Thank you for the link. That's exactly what I'm looking for.

Originally Posted by umd
I guess I just don't understand the point of this. The disadvantages of both cables and electronics but he advantages of neither.
Well, I'm still rocking an 8-speed drive train with down tube shifters. I really don't mind an 8-speed drive train; and to upgrade to a cable based STI system, would cost a pretty penny. The idea with electronic shifting is that you can cheaply (relatively speaking) put it together, and apply it to any drive train. Since the shift points are programmed into the controller, it doesn't mater if you're running a Campagnolo cassette or a Shimano cassette, you just need to tell the controller how much to move the servo arm. Plus it's fun .

Servos came in the mail; still am waiting for the batteries and voltage regulator. Hopefully, I'll have the thing shifting by the end of this week.
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